3400 RIVERFRONT BLVD Geotech Report 2022-10-25

• • • a maximum uncompacted thickness of 12 inches and compacted to not less than 95 percent of • the maximum dry density as determined by ASTM D 1557. • 6.10 CEMENT AMENDMENT • As an alternative to the use of imported granular material, an experienced contractor may be • able to amend the on-site soil with portland cement to obtain suitable support properties. It is • generally less costly to amend on-site soil than to remove and replace soft soil with granular • material. Successful use of cement amendment depends on the use of correct mixing techniques, soil moisture content, and amendment quantities. • • Specific recommendations, based on exposed site conditions, for cement amending can be • provided if necessary. However, for preliminary design purposes, we recommend a target • strength for cement-amended soils of 80 psi. The amount of cement used to achieve this target generally varies with moisture content and soil type. It is difficult to predict field performance of • soil to cement amendment due to variability in soil response, and we recommend laboratory testing to confirm expectations. Generally, 4 percent cement by weight of dry soil can be used • when the soil moisture content does not exceed approximately 20 percent. If the soil moisture content is in the range of 20 to 35 percent, 5 to 7 percent by weight of dry soil is recommended. The amount of cement added to the soil may need to be adjusted based on field observations • and performance. Moreover, depending on the time of year and moisture content levels during • amendment, water may need to be applied during tilling to appropriately condition the soil • moisture content. The amount of cement used during treatment should be based on an assumed soil dry unit weight of 100 pcf. • • Typically, a minimum curing of four days is required between treatment and construction traffic • access. Portland cement-amended soil is hard and has low permeability. Therefore, this soil • does not drain well, nor is it suitable for planting. Future planted areas should not be cement amended (if practical) or accommodations should be planned for drainage and planting. Cement amendment should not be used if runoff during construction cannot be directed away from • adjacent wetlands. It is not possible to amend soil during heavy or continuous rainfall. • 6.11 DRAINAGE CONSIDERATIONS 6.11.1 Site Drainage 4111 We recommend that roof drains be connected to a tight line leading to stormwater facilities. • Pavement surfaces and open space areas should be sloped such that surface water runoff is collected and routed to suitable discharge points. We also recommend that the ground surface • adjacent to buildings be sloped to facilitate positive drainage away from the buildings. • • 6.11.2 Temporary Drainage • During grading at the site, the contractor should be made responsible for temporary drainage of • surface water as necessary to prevent standing water and/or erosion at the working surface. During rough and finished grading of the building sites, the contractor should keep all footing • excavations and building pads free of water. • • • • G EODESIGN`' 18 Polygon-128-01:091615 •